Liquid brakes



June 20, 1961 R. GASSOT 2,989,151

LIQUID BRAKES Filed Feb. 11, 1958 ll 3 4 2 I7 I I6 I5 .3 I; FIG.2 3| 7 IFIG. 5

United States Patent '0 2,989,151 LIQUID BRAKES Ren Gassot, 8 bis, VillaCollet, Paris, France Filed Feb. 11, 1958, Ser. No. 714,649 Claimspriority, application France Feb. 19, 1957 3 'Claims. (Cl. 188-90) Theobject of this invention is to provide certain improvements in the typeof fluid brake described in the applicants earlier US. Patent No.2,750,008 wherein there is shown (see FIG. 3, reference numeral 17) apiston which compensates for the difference in volume which occurs inthe control duct whenever one of the driven pistons of a vane is pushedback into the control duct.

This compensating piston is difiicult to construct, and must in any casebe capable of extremely rapid movements. The vanes illustrated arepushed back into their housings by the liquid pressure in the brakingduct, this pressure being exerted on only one side of the vanes andbeing so high that it may damage the vanes and their housings. Theimprovements of the present invention overcome these tWo objections.

In order that the nature of the improvements may be readily ascertained,an embodiment of liquid brake in accordance therewith is hereinafterparticularly described with reference to the accompanying drawings,wherein:

FIG. 1 is a vertical section through the fluid brake.

FIG. 2 is a side elevation of a vane, to a larger scale.

FIG. 3 is a part section, taken in a radial plane of the brake, to showmechanical locking means.

FIG. 4 is a part section, taken in a radial plane of the brake, to showbraking pressure control means.

FIG. 5 is a cross-section of a portion of the vane, to an enlargedscale.

The brake shown in FIG. 1 has a cylindrical stator 1 and a rotor 2coaxial therewith, an annular channel 3 defined between them beingfilled with liquid.

In the stator are provided three arcuate passages symmetrically disposedand serving as housings for three arcuate vanes 4, 4 4 which have asliding fit in their respective passages. The arcuate passages open intothe channel 3, and their vanes are movable to bring one end out into thechannel 3. The vanes are symmetrically disposed on the circumference ofthe stator.

In the stator are also formed three linear bores serving as cylindersfor three pistons 5, 5 5 including slidable seals 45 which each engageby a tenon into a recess 40 at that end of one of the arcuate vaneswhich can emerge into channel 3. Each piston is sealed in its cylinderby a suitable packing. The inner ends of the three cylinders open into acommon fluid conduit 7. It will be seen that liquid pressure applied inconduit 7 will drive the pistons 5, 5 5 outwardly and cause acorresponding arcuate movement of the associated vanes, bringing one endof each vane into the channel 3.

On the rotor 2 is mounted a radially inwards projecting member 6constituted by forward and rear radiallyacting cams and between them aportion which forms a sliding seal with the stator and thus serveseffectively to close the channel 3. The intermediate portion between thecams is long enough to close both ends of an arcuate passagesimultaneously.

During rotation of the rotor as the portion 6 rides past each vanepositioned with one end in the channel, the forward cam (considered inthe direction of rotation) drives the vane back into its arcuatehousing. At the same time the rear cam allows the adjustment vane toemerge by a corresponding amount from its housing. Thus the inward andoutward movements of the cams always compensate for each other, andthere is no to and fro movement of liquid transmitted back into thebraking 2,989,151. Patented June 20, 1961 pressure conduit 7. Duringthis corresponding inward and outward movement of any two of the vanes,the third vane remains out to a predetermined amount to brake the liquidflow in channel 3 to the desired extent.

To permit escape of liquid from the arcuate housing of the particularvane being driven back in, there is provided a recess 32 in the sealingportion of projection 6.

Each vane 4, 4 4 has a number of liquid flow grooves formed in it toease its movement in its arcuate passage, see FIG. 2. The vane has sixgrooves in all, 8, 9, 10, 11, 12 and 13. Fig. 5 is a crosssectional viewshowing the configuration of representative grooves 10 and 13. Groove 10on one face is connected to groove 8 on the other face by a passage 29and to groove 9 on the other face by a passage 29 Groove 13 on one faceis connected by a passage 30 to groove 11 on the other face, and by apassage 30 to groove 12 on the other face.

When the rotor 2 rotates and there is liquid in channel 3, this liquidis driven round by projection 6. When any vane 4, 4 or 4 is raised intochannel 3, a circumferentially-acting force is exerted on the vane andsuch force would tend to join the vane in its arcuate passage. However,any liquid pressure exerted on one side of the vane Will (according tothe direction of rotation) be transferred through the vane so as to actin opposite direction between the vane and its passage walls, i.e.liquid pressure applied in grooves 8 or 9 transmitted to groove 10, andthat applied to grooves 11 or 12 is transmitted to groove 13. Thisensures that the vanes do not join, and remain readily movable under thecontrol of their respective pistons.

The thrusts exerted on the ends of the vanes 4, 4 4 by the liquid underpressure in channel 3 (if such vanes were perfectly symmetrical) wouldbe equal and opposite and the vanes would not tend to shift. However,one end of each vane is provided with a lug 14, making themunsymmetrical. There is thus an excess of force exerted by the liquid inchannel 3 on one end of the vane, and this is balanced by the outwardthrust of the respective control piston 5, 5 or 5 Accordingly, for agiven thrust exerted on the piston, the associated vane moves out intothe channel 3 until the forces on it are balanced. So long as suchthrust is exerted on the piston, the vanes provide a constant pressurein the channel 3,

despite any variations of speed of rotation or viscosity.

The construction need not be limited to a single projection 6 and asingle set of three vanes 4, 4 4 More than one projection 6 could beused, in conjunction with a corresponding number of sets of three vanes.

To permit use of more than one projection 6 it is desirable to be ableto reduce the total length of each projection. For this purpose the endof each vane passage remote from the associated piston may be closed, inwhich case the intermediate sealing portion of the projection 6 may bereduced in length to the width of the end of the vanes. Liquid can stillcirculate in the vane passages, because of existence of the passages 29,29 and 30, 30

It is desirable to obtain a mechanical locking action of the rotor tothe stator when they are relatively stationary. For this purpose, seeFIG. 3, there is provided a iston 31 having its smaller end engagedthrough a packing gland into the brake-pressure liquid conduit 7. Alarger head 15 on this piston is engaged in a cylinder bore in thestator 1 opening through a hole 17 into channel 3. A compression spring16 tends to force the piston downwards in FIG. 3. When braking pressureis exerted on the liquid in conduit 7, although this might tend to liftthe piston 31, there is at the same time an increase of pressure inchannel 3 which acts on the larger piston 15 so that the pistons 31, 15do not lift. As there may be a slight delay in build up of increasedpressure in channel 3, when braking pressure is applied in conduit 7,the hole 17 is made relatively small to prevent rapid outflow of liquidso that the pistons 31, 15 cannot rise very far during that delay.

When rotation stops, the pressure in channel 3 falls considerably, sothat if braking pressure is maintained in conduit 7, the pistons 31, 15will eventually be able to rise. On piston 31 is mounted a cross-barcarrying teeth 18, 18 which are then moved into mesh with other teeth19, 19 on the rotor, whereby the rotor becomes locked to the stator.When braking pressure is removed from conduit 7, the spring 16 drivespistons 31, 15 downwardly and disengages teeth 18, 18 and 19, 19

It is also desirable that the brake shall act automatically in case ofrupture of the control ducts. For this purpose there is provided thearrangement of FIG. 4. In a cylinder bore 25 in the rotor 1 is slidablysealed a piston 20 urged downwardly by a compression spring 21. The rodof the piston is slidably sealed in a narrower cylinder bore connectedto the braking conduit 7. This downward pressure exerted by the springis sufficient to cause maximum braking pressure in conduit 7.

For normal control of the brake by an operator, there is provided acylinder 22 housing a slidable piston 23 urged inwardly by a spring 24and under the action of a foot pedal 27 having a camming portion 28acting on the piston rod. The cylinder bores 25 and 22 are incommunication and are liquid filled. With no pressure exerted on thepedal, spring 24 pushes piston 23 inwardly and thus lifts piston 20against its spring 21, so that no braking pressure is exerted in conduit7. When pressure is applied on the pedal 27, the piston 23 movescorrespondingly outward, allowing piston 20 to descend and exert brakingpressure in conduit 7.

If there should be either a rupture or a leak in the bores 25, 22, thepiston 20 will no longer be held up and automatically sets the brakefully on.

I claim:

1. A liquid brake comprising a central stationary part, a revolvingrotor drum surrounding the stationary part and defining therewith a ductfilled with fluid, at least one projection dividing said duct intosections, said projection comprising a forward and rear cam on therevolving part, an arcuate recess in said projection between saidforward and rear earns, a plurality of arcuate passages symmetricallydisposed in said stationary part, each of said passages communicatingwith said duct, an arcuate vane slidably disposed in each of saidpassages, each of said vanes having a first and second set of groovesdisposed in opposite arcuate faces thereof, each of said sets comprisingthree separate grooves, a first passage through said vane for connectingthe two outer grooves of said first set with the inner groove of saidsecond set, a second passage through said vane for connecting the twoouter grooves of said second set with the inner groove of said firstset, said vanes being movable partially out of said arcuate passages soas to have one end disposed in said duct, a plurality of cylinder boresequal in number to said vanes located in said stationary part, saidcylinder bores communicating with a common liquid conduit, a movablepiston within each of said cylinder bores, means for coupling a separateone of said pistons to one end of each of said vanes, and a means forapplying pressure to the liquid in said common conduit for moving saidpistons to force said one end of said vanes into said duct, the cams ofsaid projection being disposed so that the forward cam pushes said oneend of one of said vanes into its arcuate passage while the rear campermits the said one end of the following vane to emerge from itsarcuate passage to a corresponding extent.

2. The apparatus of claim 1 wherein the central stationary part includesa radial two-part cylinder bore having a part of greater diameter and apart of smaller diameter, the smaller part communicating with saidcommon conduit and the larger part communicating with said duct, atwo-part piston of corresponding diameters in said bore, firstradially-inwards facing teeth on said rotor drum, secondradially-outwards facing teeth on said twopart piston positioned toengage with said first teeth and spring means in the bore serving tourge the piston in the direction to separate said teeth.

3. A liquid brake comprising a cylindrical stator, a rotor drum disposedcoaxially with and rotatable about the stator, said rotor defining withthe stator an annular channel filled with liquid, a projection on theinternal circumference of the rotor, said projection having forward andrear radially-acting cams and a part between said two cams forming asliding seal with the stator, said stator including three arcuatepassages opening into the channel defined between the stator and rotor,three arcuate vanes disposed slidably one in each arcuate passage andbeing movable partially out of their passages so as to have one enddisposed in the channel, each vane having longitudinal grooves in itsopposed arcuate faces and internal passages forming a communicationbetween grooves on said opposed faces for balancing of liquid pressureat each arcuate face of the vane, the vanes being symmetrically spacedon the circumference of the stator and the dimensions of the forward andrear cams being such that as one cam pushes a vane back into its passagethe other cam permits another vane to emerge from its passage to acorresponding extent, said stator including three cylinder borescommunicating with a common conduit, three pistons disposed one in eachbore and each coupled to that end of a vane which is movable into thechannel, liquid in the cylinder bores and common conduit, means forapplying pressure to the liquid in said common conduit for moving thepistons to force an end of each vane into the channel, the statorincluding a radial two-part cylinder bore having a part of greaterdiameter and a part of smaller diameter, the smaller part communicatingwith the common conduit and the larger part communicating with thechannel, a two-part piston of corresponding diameters in said bore,first radiallyinwards facing teeth on the rotor, secondradially-outwards facing teeth on the two-part piston positioned toengage with said'first teeth, and spring means in the bore serving tourge the piston in the direction to separate said teeth.

References Cited in the file of this patent UNITED STATES PATENTS1,631,800 Dotsch June 7, 1927 1,939,605 Dempsey Dec. 12, 1933 2,177,511Aikman Oct. 24, 1939 2,750,008 'Gassot June 12, 1956

